zen-cli command getscinfo: add support for filter out ceased sidechains and for pagination

[paolocappelletti]

zen-cli rpc command getscinfo (when invoked without a specific scid) should support optional parameters for filter out ceased sidechains and limit the response array:

• onlyAlive (boolean - default false) : if set to true the CEASED sidechains are filtered from the result
• from (integer) : if set, limit the starting item index in the result array to this (included) (0 based)
• to (integer) : if set, limit the ending item index in the result array to this (excluded) (0 based)

To be coherent with the new explorer endpoint, the result should also be changed to this format:

{
"totalItems":95,
"from":0,
"to":50,
"items":[
   .......
  ]
}

[abi87]

@Cermelli @annagiuliaber this can be closed down as it is already implemented in sidechains_dev